1. Field of the Invention
The present invention relates to a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller for controlling a control-processing-object material with respect to a physical state of the material over a predetermined control time period under control conditions in consecutive time divisions into which the predetermined control time period is divided. Typically, the present invention relates to a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller applied to a continuous annealing process in the steel industry.
Processes exist in which materials of different kinds are connected in series and the train of the materials is conveyed on a line to sequentially undergo heat treatment. Such processes are typified by a continuous annealing process in steel manufacture. Ordinarily, an allowable temperature range (upper limit, lower limit) and a processing time are determined with respect to each of different materials, and it is necessary for an apparatus for performing heat treatment to change controlled temperatures so that the temperature of each material is within the temperature range. The temperature increase and decrease rates in the apparatus are determined within certain limits.
In obtaining temperature transitions satisfying conditions according to temperature ranges with respect to materials, it is important to determine a suitable order (sequence) in which the materials are caused to flow on a line. To know whether temperature transitions satisfying conditions according to the temperature ranges can be made with respect to a sequence, it is necessary to evaluate the temperature transitions with respect to the sequence, that is, it is necessary to evaluate whether temperature transitions are possible such that no deviations from the temperature ranges occur (or what amount of deviation is allowable). Evaluations of temperature transitions thus obtained are reflected in total evaluations of sequences of materials (including evaluations of other restrictions) and used for the purpose of determining a suitable one of the sequences. Target temperature transitions finally obtained can be used as a temperature increasing and reducing schedule in the apparatus for heat treatment.
In conventional continuous annealing processes, finding a sequence capable of satisfying conditions according to certain temperature ranges has been intuitively performed by an expert (a master or a skilled person) on an empirical basis. A method of finding a suitable order of materials to be annealed, conventionally performed by experts, will be described concretely. For example, a displayable editable table is prepared on a screen of a PC (personal computer) by a spreadsheet program such as Excel (a registered trademark of Microsoft Corporation). In the table, materials to be annealed are related to rows (records) and the widths and thicknesses of the materials to be annealed, temperature range codes and other attribute items are related to columns (fields). The temperature range codes are numeric values, e.g., 75, 76, 86, 87, 88 . . . , and an expert grasps “75” as a temperature range [240° C.–280° C.] and “76” as a temperature range [260° C.–310° C.], for example. Also, the expert roughly grasps the degree of proximity between 75 and 76, between 86 and 87, and so on, and determines in his/her thought a sequence such that the adjacent temperature ranges overlap one another while considering other restrictions. In an ordinary steelwork, a plurality of lines (e.g., several ten lines) exist on which processes are simultaneously executed in parallel with each other, and an expert determines in which sequences on lines each of items to be annealed should be included. In the case where a need to produce an item at an urgent request arises and where the item at the urgent request is inserted in a predetermined line with priority, it is necessary to reconsider the sequence following the inserted article.
2. Description of the Related Art
Patent Document 1 discloses a batch annealing process with respect to a cast product. In the batch annealing process, a determination reference temperature transition curve is formed on the basis of an atmosphere temperature transition tendency according to an empirical rule with respect to a self-annealing box and atmosphere temperatures suitable for annealing, and actual atmosphere temperatures in the self-annealing box at a plurality of points in time in a self-annealing process are measured. The quality of annealing is determined by checking the measured temperatures against the determination reference temperature transition curve.
Published Unexamined Patent Application No. 11-291021 (Patent Document 1)
If temperature transitions satisfying conditions according to temperature ranges are possible, it is necessary to obtain such transitions (of a zero temperature deviation cost). However, if it is impossible to satisfy conditions according to the ranges, it is not necessary to obtain temperature transitions (of a minimum temperature deviation cost) by strict calculation. Finding temperature transitions satisfying conditions according to temperature ranges by changing the sequence is essentially preferable. Also, since there is a substantially high possibility of a schedule posterior with respect to time being changed afterward, it is sufficient in ordinary cases to satisfy temperature range conditions with respect to materials preceding in time with priority. With respect to items to be annealed, it is preferable to avoid changing the temperature during annealing from the viewpoint of maintaining the quality. Since there is a possibility of a sequence of materials coming after in time being changed, for example, due to occurrence of a need to process an additional item at an urgent request, it is desirable to avoid changing the temperature as long as a point in time at which it becomes impossible to satisfy temperature range conditions for items to be subsequently annealed in the order or to reach an end temperature is not reached.
In the conventional method of formation of a sequence by an expert, it is difficult for an expert to accurately determine, with respect to a sequence formed as an order of a plurality of materials to be presently annealed, whether temperature control of the entire sequence can be actually executed under temperature increase and decrease rate restrictions so as to satisfy temperature range conditions with respect to the materials to be annealed. Also, it is difficult to immediately predict when annealing on a material probable to come at a position closer to the end of an order of materials to be annealed will end.
Patent Document 1 does not present or suggest any algorithms for determination as to (a) whether, in a continuous annealing process, with respect to a sequence of steel sections in which steel sections to be annealed have different upper and lower limit temperatures in corresponding annealing periods, temperature control can be executed so as to satisfy conditions according to the upper and lower limit temperatures of each steel section to be annealed (hereinafter referred to simply as “temperature range conditions” as occasion demands), and (b), under a demand for minimizing variation in temperature in each steel section to be annealed, which is desirable from the viewpoint of improving the quality of the steel section to be annealed, how concrete controlled temperature transitions should be made with respect to the sequence of steel sections to be annealed to meet the demand while satisfying the temperature range conditions.
A process is conceivable in which a temperature transition cost is suitably defined with respect to the degree of deviation from a temperature range and temperature transitions of the lowest cost are obtained by a dynamic programming technique with respect to possible temperature ranges. To perform this process, however, there is a need to first discretize temperatures in ranges through which transitions can be made. This discretization is time-consuming and also entails a problem in terms of accuracy. If discretization is finely performed to obtain temperature values in wider ranges to improve the accuracy, the efficiency is reduced.
A first object of the present invention is to provide a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller capable of efficiently executing processing for computation of information as to whether control of a physical state of a control-processing-object material satisfying physical state range conditions with respect to time divisions is actually possible in the case where a limit heightening rate and a limit lowering rate exist and where the physical state range condition is determined with respect to each time division in a control time period.
A second object of the present invention is to provide a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller capable of efficiently computing a concrete process of transition of a physical state in which variation in the physical state in each of time divisions is limited, and also having the capability according to the first object.
A third object of the present invention is to provide a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller capable of efficiently computing a concrete process of transition of a physical state such that physical states of a control-processing-object material at a beginning time and an ending time in a control time period coincide with a given value, and also having the capability according to the second object.
A fourth object of the present invention is to provide a physical state control purpose information computation apparatus, a physical state control purpose information computation method, a physical state control purpose information computation program and a physical state controller suitable for annealing of steel, and also having the capability according to the third object.